The present invention relates to pipe couplings, and in particular to a pipe coupling having a tensioning system for applying a radial force to pipes, and for tightening the coupling around the outer surface of the pipes.
A wide variety of pipe couplings for connecting together two pipe ends in a fluid tight manner are known. In order to enable the coupling to function for slightly undersized and slightly oversized pipes, a longitudinal gap between free ends of the casing of the pipe coupling is required.
One known example of a pipe coupling for connecting together two plain-ended pipes in a fluid-tight manner comprises a tubular casing formed with a longitudinal gap, a sealing gasket of resilient flexible material typically of rubber or synthetic rubber, arranged within the casing, and tensioning means for reducing the width of the longitudinal gap so as to tighten the casing around the gasket. In use, the sealing gasket is placed around the adjacent pipe ends and the tensioning means are tightened to clamp the gasket against the outer surfaces of the pipe ends to form a fluid-tight seal.
In use, the fluid pressure in a pipeline tends to deform the casing, and in particular deforms the casing in the region of the free ends on either side of the longitudinal gap. The deformation of the casing reduces the forces acting on the gasket in the region of the free ends. The reduction in forces acting on the gasket decreases the maximum rated fluid pressure for the pipe coupling. In known pipe couplings, additional reinforcing material, additional welding and large and relatively heavy trunnion bar mechanisms have been used to counteract the deformation of the casing and the resultant reduction in forces acting on the sealing gasket.
It would therefore be desirable to provide a novel pipe coupling having improved resistance to deformation in the region of the free ends of the casing, and thus improved resistance to fluid pressure. It would be particularly desirable to provide such a pipe coupling that is lighter, smaller and less expensive to manufacture than pipe couplings having equivalent fluid pressure ratings.